A conventional practice has been to apply a rubber base sealing material to the inner surface of a pneumatic tire beforehand for the purpose of causing a puncture hole to be sealed off naturally in a case where a pneumatic tire goes flat.
Rubber base sealing materials are sealing materials (what is termed as raw rubber) obtained by compounding various compounding ingredients to rubber. There have been a variety of rubber base sealing materials proposed heretofore. For example, Japanese patent application Kokai publication No. Sho. 53-55802 has disclosed a rubber base sealing for preventing a tire from being flat out, which comprises polyisobutylene, an inorganic filler and peroxide.
However, the rubber base sealing materials have a higher viscosity (for example, in a case of a sealing material made of butyl rubber, its viscosity is approximately 80 Pa·s/100° C.). Each rubber base sealing material can not be applied to a surface (the inner surface of a pneumatic tire), which is intended to be coated with the rubber base sealing material, by a spray coating process, and resultantly the rubber base sealing material has to be applied manually. For this reason, the rubber base sealing material has had a disadvantage of having poor workability, and causing unevenness of coating easily, and making it impossible to secure a neat, evenly-coated surface.
In addition, if the viscosity of each rubber base sealing material is intended to be decreased through adding a large amount of an organic solvent to the rubber base sealing material for the purpose of making it easy to apply the rubber base sealing material by a spray coating process, the organic solvent has a disadvantage of bringing an adverse effect to the working environment.